Regenerative transistor amplifier



Feb. 23, 1954 J. H. FELKER 2,670,445

REGENERATIVE TRANSISTOR AMPLIFIER' Filed Nov. e. 1951 4 sheets-snee*` 1 /NPUT- ooUTPUT /9 /2 /3 2/ L 25J L /4 v6 olif 2'4/ -I- T/a. /5f TQ/7 26 I j RESET ln PULSE "11 Re Rc Pm I, W\ Wb w@ F/G /B e R Ve Rb c l T e A1 E/G. /c

rPEA/r Po//vT vv e L l |\|441.LEYPo//vr "HT F/G. /D

PEAK Pol/v r\ 'c/kVAL/.EV POINT /N VE /V TOR Feb. z3, 1954 J. H. FELKER 2,670,445

REGENERATIVE TRANSISTOR AMPLIFIER Filed NOV. 6, 1951 4 Sheets-Sheet 2 22 23 F lG. 2A 32 f v /NPUT f OUTPUT /2 /a /34 f 25% /9 /4 V35 n/5 /7\ 24 f (L 30 T .37 T f@ Tf@ I P MT PST RESET 26 PULSE F lG. 2B AsL' GPOUNLL/ 1 ,lh- Las/new-j L l COLLECTOR F/G. 3A

B OUTPUT c ,4/vo L OP I OUTPUT ANO F/G. 3C

OUTPUT VVE/V705J B H. FEL K E R ATTORNEY Feb. 23, 1954 J. H. FELKr-:R 2,670,445

REGENERATIVE TRANSISTOR AMPLIFIER Filed NOV. 6, 1951 4 Sheets-Sheet 3 ATTORNE Y Feb. 23, 1954 J. H. FELKER 2,670,445

REGENERATIVE TRANSISTOR AMPLIFIER Filed NOV. 6, 1951 4 Sheets-Sheet 4 OUTPUT DOUJL /NH/B/ TOR FIG. 6A

A I OUTPUT Kn l- /NH/B/TOR DF vu CLOCK# vu /NPur A /NPUT B /NPUT c FIG 6B D /NH//roR o I L n OurPu n n H. FEL KEA Bmg/M Patented Feb. 23, 1954 REGENERATIVE TRANSISTOR AMPLIFIER Jean H. Felker, Livingston, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application November 6, 1951, Serial No. 255,043

7 Claims. l

This invention relates generally to transistor pulse ampliers and more particularly, although not exclusively, to transistor pulse ampliers suitable for use in high-speed switching systems and computers.

The principal object of the invention is to amplify and reshape low-level pulse type signals.

A related object is to provide a high-speed transistor amplier of suii'icient flexibility for use everywhere that gain is required in a pulse-operated switching system or computer.

In its principal aspect, the present invention takes the form of a regenerative pulse amplifier comprising a single-transistor flip-flop circuit which is triggered to its high current state by signal pulses fed to the transistor emitter and is reset to its low current state by a regular succession of pulses fed to the transistor base. The amplifier is provided with a high input impedance by an emitter load-line resistor returned from the emitter to a direct potential of the polarity required to bias that electrode in the so-called forward direction, while high current gain is obtained by using the negative input impedance of the transistor to switch to the 10W impedance provided by a crystal diode returned from the emitter to another direct potential. The two direct potentials mentioned are chosen so that one is above and the other is below the quiescent level of the transistor base and are generally of opposite polarity. The reset pulses applied to the transistor base provide high-speed operation and control the onset and the duration of the pulses generated by the amplifier, making the output pulses substantially independent of the transistor and circuit parameters and the shape of the input pulses.

The invention also features a crystal diode which is poled oppositely to the direction of positive emitter current iiow connected in series between the signal pulse input terminal and the emitter to isolate the emitter circuit from the preceding circuits and, in conjunction with the other diode connected to the emitter, to provide direct-current restoration of incoming signal pulses. Direct-current restoration forces the signal input pulses always to start from a predetermined direct voltage level and enhances thereliability and accuracy of the amplifien'while isolation of the emitter circuit frees the signal input terminal from any requirement of following the excursions in potential of the emitter once the circuit has been triggered.

Transistor pulse amplifiers embodying the present invention are particularly adaptable for use in high-speed switching and digital computer systems. They are capable of generating standardized pulses of uniform amplitude in response to input pulses which exceed a minimum threshold level. They are also capable of the basic operation in computer applications of inhibition; that is, their normal operation of generating pulses under the control of signal pulses can be inhibited by the application of suitable inhibiting pulses. In accordance with a feature of the invention, inhibiting pulses may be applied to the transistor base in the intervals between reset pulses to prevent the generation of output pulses during these intervals.

A more thorough understanding of the invention may be secured from a study of the following description of several specific embodiments. In the drawings:

Fig. 1A is a schematic diagram of a regenerative transistor pulse amplier embodying the invention;

Fig. 1B is a conventional transistor equivalent circuit;

Fig. 1C is a simplied emitter-current versus emitter-voltage characteristic;

Fig. 1D illustrates the actual emitter-voltage versus emitter-current characteristic and the emitter load-line of the circuit shown in Fig. 1A;

Fig. 2A is a schematic diagram of a variation of the embodiment of the invention shown in Fig. 1A;

Fig. 2B illustrates wave forms appearing in the circuit shown in Fig. 2A;

Figs. 3A, 3B, and 3C are block diagrams of several common logic circuits for digital computer use;

Fig. 4A is a schematic diagram of several basic digital computer components embodying the present invention, including logic circuits corresponding to those illustrated in Figs. 3A, 3B, and 3C;

Fig. 4B illustrates input and output pulse trains found in the circuit shown in Fig. 4A;

Fig. 5 is a. block diagram of a logic circuit which has the property of inhibition;

Fig. 6A is a schematic diagram of a three-terminal logic circuit embodying the invention to which an inhibition terminal has been added; and

Fig. 6B illustrates pulse trains found in the circuit shown in Fig. 6A.

In Fig. 1A, the transistor H possesses an emit- Y ter electrode I2, a collector electrode I?, and a tery and rectifier polarities are chosen for therindicated direction of positive emitter current. flow. The illustrated embodiments of the invention are not, however, limited: toany particular type i transistor. For positive emitter: current ow in the opposite direction, all battery/and rectier polarities are reversed fronrthose--shown in the drawings.

In Fig. 1A, a base resistor I5 is connected be-y tween the base of transistor, I l and ground, While a load resistor' it: is' returned; :fromthe collector to` anegative voltage, conventionally represented-z by battery il, which serves to` biaszthe` collector in theV so-called reverse direction.- The: emitter` is: returnedA to a. positive potential, represented by battery i8, through a1loadline. resistor; i9,

the resistance of which: is largey in` comparisonY with the internal emitter, resistance of transistor Il. small.. negative potential, represented. by battery 20", through. a, crystal diode 211 which is poled in the direction-ofV positive emitter current. flow.. Signal input pulses are appliedto the emitter of transistor il through-.a coupling condenser. 22 and a crystal diode 23. Diode 23 is poled` op.- positely to the direction of positive emitter currentfflow, and the junction between condenser 22 andvdiode 23..is returned toa negative potential, representedby battery. 24,' through another large resistor 25. Output pulses are taken fromthe collector, and reset pulses are applied to the base through, a` crystal diodeZSY which is poled for easy current ow toward that electrode,

The operation ofthe embodiment of the invention shown in Fig. 1A may best be explained in` connection with Figs. 1B, 1C,` and 1D.l The conventional transistor equivalent circuit shown in' Fig. 1B comprisesa T-network made up of the internal transistor emitter, collector, and base impedances Re, Rc, and Rb. An equivalent generator Rmle is in series with Re, and a-load-line resistance RL and aA negative collector voltage supply Vee are in series between that element-and Rb; In the equivalent generator,` Rm designates the transistor mutual impedance, and le representsthe emitter current. Thevernitter voltage Ve is, as indicated, that applied between Re and Rb.

Fig. 1C is a greatly simplified illustration of the transistor emitter characteristic for a current gain (a) greater-than unity and a high baseimpedance. The curve is approximate and is based on a number of assumptions about the relative magnitudes-of the transistorparameters. These assumptions, known-as the brokenline assumptions, are:

(l) Re, the emitter impedance, is high andA constant (comparable to the back impedance of a diode) when negative emitter currentows and low and constant (comparableto the forwardim'- pedance of a diode) when positive emitter current flows.

(ZlRb, thel base impedance, is constant.

(3)- Re, the collectory impedance', is'hgh' and In addition, the` emitter is returned to. a`

constant for negative or positive emitter currents unless the unit is saturated, in which case the collector impedance drops to a constant value of the same order as the emitter impedance.

(4) Rm, the mutual impedance, is zero for negative emitter current and constant and greater than Re for positive emitter current unless the unit is saturated, in which case Rm is zero.

The; most; significant. featurefi of the: emitter characteristic is the pealew/'o-ltage;` the voltage, that is, at which the input resistance becomes negative. The peak voltage is generally negative; ande the. peak point is reached after the current gain becomes greater than unity, which generally:V assumed' to occur when the emitter current ceases turbe; negative and becomes positive: While there is 'some evidence that the peak pointmay not? be reached until the emitter current is positive, in any event, the peak point is a iirsty order eiect of the base impedance and the collector current thatlflows when the emitter current: isazero.

Another signicantfpointhonthe emitter:char-w acteristic'is the: valley point', the-.point-atfwliicliff thetransistor saturated Asl thezemitterl current is increased, the collector current increases-at'i a morerapid rateiif: a isgreater'tlian unity-i?, and

the resulting base current? carriesY tlieinternal-1 emitter-base-collector node negative.Y Ait the same time, the collector. current: carries the-exeternal collector terminal: in a: positive directionY towards ground; When: the internal node:has

fallen; to: a voltage near: that off the collector terminal', the valley.y pointt has been reached;i and@ the'transistor is said tof-be saturated. 'Izlielt'ranA` sister.V has in. effect. become a passivenetwork` becausev theY holes emittedf atf-the emitter.' have-y reducedithe effective collector impedance` toaminimum. value, andi-Rm` has 'therefor-cheer; made zero.. Further incrementsinthe-emitter-current= divide between` the base and collector circuits in, accordance with'` their. impedance-levelscandf require that the emitter` move: positive.

Approximateexpressionsfor thevalleyy vcfltageL n and currentbased upon the-broken-line;assump tionsare:

where-ic is the instantaneousV coilectnrcurrent.

andis is the instantaneous 'emitter'current' The emitter-voltage versus emitter-current curve showniinl Fig. 1D is aY moreaccurate representation ofthe emitter characteristic of.J the embodiment' of the inventionillustrated* in Fig:

1A; rlhe pealcpoint is' belowthe'l axis; andi the emitterload-lines providedU byresistor lil`-A andHdiode-ill areshown; The steep Iload-line'. to the Vleft isprovided by 'resistor I9, the slbpe der pending; upon` its resistance` and* the interception s intercept being determined by the voltage supplied by battery 2D. The magnitudes of the voltages supplied by batteries I8 and 20 are selected so that, as indicated, the load-lines of resistor I9 and diode 2I intersect just to the right of and above the negatively sloped portion of the emitter characteristic, the load-line of diode 2| intersecting the positively sloped portion of the emitter characteristic in the positive current region and the load-line of diode 2| intersecting the Ve axis below the peak point of the emitter characteristic. v

In the embodiment of the invention shownin Fig. 1A, resistors I9 and 25 are chosen so that, in the absence of emitter current, the emitter of transistor I| rests at a voltage below the bias on diode 2|. This is point A in Fig. 1D. kWhen thev input goes above the peak point, diodes 2| and 23 are cut ou, and the current set by resistor I 9 begins to flow into the emitter. Because of the negative input impedance, the positive emitter current causes the emitter voltage to fall towards C. If the negative resistance is high enough and the unit has sufcient high frequency gain, the emitter current will snap out to point B. The circuit will then stay locked up at B indefinitely unless the emitter is pulled below the valley point C or the base is pushed positive. It will be noted that Abecause of the negative impedance at the emitter, the load-line can be switched from a high impedance offered by resistor I9 to the low impedance oiered by diode 2l when conducting. This gives the circuit a large current gain at the emitter. The emitter current is multiplied by the current gain of the transistor Il to give a large practical current gain at the collector. The minimum triggering `current is iniiuenced by the slope of the curve between points A and C. It will be noted in this connection that if the load-line of resistor IS does not intersect the load-line of diode 2| before it intersects the transistor emitter characteristic, in situations involving transistors with restricted band widths the transistor will not operate beyond the negative impedance portion of the characteristic, and the collector signal will be very small.

. The circuit which has been described is actually a nip-flop circuit rather than an amplifier. In order to make it an amplifier, it is customary to replace diode 2| with a capacitor. If that is done, when the emitter current has snapped out to line DC, the capacitor charges down line DC. When the emitter voltage reaches the Valley point, the current snaps to the low current state, the capacitor discharges to A, and the unit locks in at the low current state. Thus, the circuit develops an output pulse in return for each input triggered. There are at least two disadvantages to using a condenser to provide automatic cut-off in high-speed application. One is that the duration of the output pulse depends upon the slope of the transistor characteristic between points C and D. Another is that in triggering the circuit the condenser must be charged from voltage A to the peak point. This means that if signiicant delays are to be avoided in high-speed applications, a larger triggering current is required than when diode 2| is used. The circuits shown in Fig. 1A can be triggered by a quarter of a milliampere without delays significant to a computer operating at a megacycle rate.

Turning oi the circuit shown in Fig. 1A by a voltagevapplied at the emitter -is extremely difcult, since the emitter has to be pulled negative to the valley voltage and the voltage drop has to be developed across the low impedance of conducting diode 2|. However, the circuit can be shut oi by a positive reset pulse appliedr at the base of transistor II throughrdiode 2I.`

It will be seen that transistor II can go to its high current state in this circuit only when the reset pulse is not present and will always be driven back to the low current state by the next reset pulse which is applied to the base. Therefore, the onset and the duration of each output pulse are under the control of the reset pulses and are substantiallyv independent of the tran-V sistor, the shape o-f the input pulses, and the circuit parameters.

This feature of the present invention makesA it a very simple matter to obtain the rigid synchronism required in a serial computer or switching system. Sine wave clock signals are applied to thebases of the transistor ampliers through diodes. The phase of the signal fed to the base of each amplifier is chosen so that the potential of that electrode will fall to ground just after the latest time at which an input pulse, if present at all, could have risen. Then the output, if any, is in synchronism with the clock and not the input. The circuit is, therefore, a pulse standardizer as well as an amplifier.

The presence of diodes 2| and 23 also provides Y versus emitter-current characteristic at a highv current point, but it also acts with diode 23 in providing direct-current restoration of the incoming pulses. Condenser 22 may, of course, beV omitted if the incoming pulses are already at the desired direct voltage level, since its principal purpose is to isolate the circuit oftransistor from the direct voltage level of the incoming signal pulses. Diode 23, on the other hand, serves to isolate the flip-flop circuit associated with transistor II from preceding circuits by freeing the input terminal from any necessity of following the emitter on its negative excursions. In

other words, when the emitter snaps negative,'it

Will not drag down the input voltage, which is free to continue to rise.

A variation of the embodiment of the invention shown in Fig. 1A is illustrated schematically in Fig. 2A. In the circuit of Fig. 2A, a crystal diode 30, poled for easy current flow toward the base electrode of transistor II, is connected in series between base resistor I5 and ground to present a high base impedance when the transistor base is driven positive and to present a low impedance when the transistor is triggered. Diode 3% is shunted by a resistor 3| to provide a path for discharging stray capacities.

The initial elements of a typical load for highspeed switching and digital computer applications of the present invention is shown to the right of load resistor I6 in Fig. 2A. Speciiically, a coupling condenser 32 is connected between the collector of transistor. II and the terminal Wlicliis'for convenience; termedi theL outputA terminal.2 From-the output terminali a; large re sister Sisreturnedr toa negativelpotentialg'- con ventionally-represented by battery 35; andiacrys tali diode 35i. pold' for" easyf current 'new from-' ground `rtoward the output; termina-1i isfreturneelitofa\ negative potential representediby# batteryff 31 type of? load providesL directecurr'ent restoration of `theoutput signal so -tliat the `pulses goingto= then'eX-t Vdiode 'networkfwill always starte at? theV level` xed" by batteryy 311i In addition; when1- conducting, diodeIl t'provides'a very low load impedance for" theA transistor`` when it rst starts toilip-tolthe high current' state; speeding' upthe'regenerativeoperation. Oncet-he'collectorV Voltage has risen appreciably, diode-3S^is .cut-citi Al'few of"tlie'more'irnportant Wave-forms found inthe embodiment ofthe invention-shown inlig;v 2A" appearI irr 2B;- wherevoltage is* plotted' aga-inst time. The upper curve illustrates the# wave-form appearing at the-base; A' sinewave ofsuitalole-V frequencyN (one megacycle, for exif ample); applied* throughl diode: 2T# produces the` trainof positive reset orelockf pulses shown, and@ the-transistor base-- goes slightlyA negative during tliepassage-offeaeh emit-terV current pulse. The. middl'ecurveillustratest-he emitter Vvoltage-Wave form; whilet-he-lowercurvedepicts the collectorvoltageWave form; As shown, only theesig-nal atltheemtter canproducean output pulse; and iii-can` produce-one onlyduring'- the' intervals setVr by tliebase onclock signal.' in. thea-bsence o a basepulse, the cir-cuitv is triggered to its high' current statewhen the emitter voltage reaches'I the peak point; Theernit-ter'voltage falls t'othe value indicatedEV icyk point-B f in Fig. 1D with the triggering,` and= thecolleetor voltage pulseI continues" untilk thevbase is-Y drivenpositiveV byf the next clock pulse;4

By way of example, the following li'stfof circuitparameters' for the circuit of Fig. ZAYiS-given asA being" typical for many embodiments of the invention- Resistor T'. 470' ohms. Resistor i6 470 ohms.,v Battery Il. -8 volts. Battery I8 +12 volts. Resistor IB 24,000 ohms. Battery. ZEL -l` Volt. Condenser. 22 0101' microfarad Battery 24 -8vo1ts. Resistor 25 39'00 ohms.4 Resistor 31. 5.1'0'0 ohms. Condenseri 0.011 microfsrad'. Resistor. 34 10,000 ohms. Battery 35 -2'4 Volts. Battery 3'! -2vo1t`s.

The -variousrectiers may botany suitable `crystal diodesorother asyirlmetricallyy conducting: de@- vices, and transistor` il ispreferably aA unit hayin'gra value of. a of the order of. 2:

As .has .been indicated, .the embodimentsv ofV theA v invention illustrated inlFigs. 1A: and .2A areipars-v tioularly adaptable .foriuse in. high-speed switch inga or. digital computerk systems. 1t'. is possible; for example, tot construct a digital. computer in which.: all.' logic operations are performed in; pas;- sive diode circuits and inwhiclrr active elements' are'. usedionly as gain producingV devices. to: make up for attenuation. in. the diodel circuits.. rIhe regenerative pulse amplifiers. shown in Figs. 1A andfrm'ay be. employed; advantageously, for that.

purposei` Fig-51-32A.. 3B, and 3C are blockl diagrams' ot sofi three common legit eircuitsi 'melone' n Ergnicompriseslinputterminals labelediA B', andfG';

a so-called- AN-DL" circuit lill; arramplier #It endian outputlterminalf andi-develops an output-f only1` if-"alltliree1or its@ input terminalsA are energite'dl- 'I'Lleicireuitvin Fig; 3Blcompr-isessimilar-f input terminals labeledA; B, andiC', AND-circuits'- 423; til, and 4l; 'one'fr eaclrpairofnputftermiw nal's;.a-secall'ed OR-"circuit 45,- an ampliii'er- 41% andt an output-terminale ande developswv an output Whenever at least two of? its; three inputs'- are energized. The one in Fig. 3C comprisesvinputf terminalsf-la-loelednlll; B, andG, a-n'f@R: circuit 4G, an amplifier'li-L and an output terrninah` Inf# these-diagrams; ais-hasL beerr indicated; circuit is one` which deyel`cms-1-aI-nM output'-pulse-r only` when* all` of its inputsf. are` energized", WhileI` an GR" circuit' is one Wliichdevelops ant-output" When any one ofvr its inputs ist energized?. Il? Willi benoted4f that-- tlielsame amplier circuit may liet used i in all three of i"'tloe circuits villustrated."

Fig. 4A'- i`sfasci'iematie'l diagram ofi afspecie" computerr componentlero'loodying the `presentf-iir--v vention Whiehfincludes@ portions corresponding to respective-onesof`tlie logiecircuitsillustratedin Figs. BA1, BBga/nd 3.' It? will beseen that! thev circuit-shown in Fig. @A isroughly dividedi intov threey sections;- the i`rst-0rfupper AoneA corresponda'to-the bloeit diagram5V shown in Fig.r 31A2 the second ori middle one. corresponds tothe. block diagram' shown-iin Fig; 3B', Whilathethird or lower one correspondsI tothe block; diagram. shown in Fig; 3C. Amplifiers-1corresponding. to'.` the regenerative pulse amplierfsliownz in Fi'gsf...

. l-A and 2A are1 usedf asthe. active. elementszin: all;

three sections.

Iii-Fig. 4A, the inputlterminaslaheledl Ag.B; and` C Y are connected' to: coupling;v conden'sersf` 5tlg. 52T, and-`53,.respectively. Acrystaldiode 54',.po1ed;. oppositely to the direction. off positive emitter" current. flow.; is connected between condenser.' 5t; and. the emitter' ofitransistorf Ifl'l in the rsit or: upper section ofthe.gurer Siin'ilenlypole1i.d::.r od'es 55S and'V 56. areiconnectedsbetween c@mienners;E 5T. and! 53,. respeetive'ly,v and.' the sameA elettrodo: The junction; betweernconden'serr 5:1? andiode: 542i is returned toanegatiye potentialg. represented;l byf abattery` 5T', througrri a. high.i resistancef, Whilethecorrespondingpointssbetween.condenseers. 5.2i and: 53 andi diodes: 5.5i. and: 5E are: returnedl totlc-ie same: potential through resistorsl 55:-"ar1dr2 6l); respectively: Diodes-.545 55;..andf aitake. thesy place ofi diode" 23:` inf. the'- regeneratiile. amplifier: circuitV Explanationiof the?. operation oit theseiaml" the; other' portions; of;` the: circuit` shownr. Eig.: may 'best be. meldet in connection: with: Fig, 45E-i: Illustrated there are: a: numberv of: wave forms-x representing r pulses which.: may; be: applied to] inly put. terminalsI A; B; C. and. pulses;` which:l appear: at' the various: output. terminala.- upon;I application oij'theI input'. pulses' shown@ Thus; when.: pulseszcorresponding to'1those'.-shownv in: the?. iirst. three lines" in Fig.. 45B: are: app-lied: to: terr minals. Af, B,..andz.'C;,a;.iseries ofi pulsescorrespond-n ing.` to those:shownai'n` the fourthline appears attire-output terminalin the first or upper sec-r tionlof thefcircnitshowrrinl'ig; 4A.. Anwoutputf pulse; isr developed; when and onlyv when aninput.; pulse is applied toall three of terminals. A,B. and C. For: example. when av positive pulse: is-` appliedl to terminal A only; diodesA 55 and` 5E are not cut off, and the limiter Will-be heldi-loelow.V thepeak point4 However-,.Wherr positiyepulses are applied.vr toall threeinput:- terminals, all. three.V

' diodes 54, 55, and 56 are cut oil, and triggering action takes place because the emitter is raised above the peak point.

In the second or middle portion of Fig. 4A, a pair of crystal diodes 6I and 62, poled oppositely to the direction of positive emitter current flow, are connected between condensers 5I and 52, respectively, and a common point which is returned to a positive potential, represented by battery 63, through a large resistance 64. That point is, in turn, connected to the junction between resistor 25 and diode 23 in the regenerative amvpliiier through a crystal diode 65 which is poled in the direction of positive emitter current flow.

A similar combination, including a pair of crystal diodes 66 and 61 which are poled oppositely to the direction of positive emitter current ow,

a resistance 68 and a battery 69, and a crystal diode 10, which is poled in the direction of positive emitter current flow, is connected between condensers 5| and 53 and the junction of resistor 25 and diode 23. Still a third such combination, including a pair of crystal diodes 1I and 12 poled oppositely to the direction of positive emitter current-flow, a resistor 13 and a battery 14, and a crystal diode 15, poled in the direction of positive emitter current ow is connected between condensers 52 and 53 and that same junction point.

The output of the second or middle section of the circuit shown in Fig. 4A is illustrated on the fth line OffFig. 4B. As shown, an output pulse is generated when a pulse is applied to any two of the input terminals. Diodes 6l and 62, 66 and 61, and 1| and 12 form AND circuits which pass pulses only when both inputs are energized. Diodes 65, 10, and 15, on the other hand, form an OR circuit which passes a pulse when any one of its inputs is energized. Thus, when an input pulse is applied only to terminal A, diodes 6I and 66 are cut off, but diodes 62 and 61 vare not. Neither AND circuit, therefore, passes the pulse.

`However, when pulses are applied to both terdenser 5l and the junction between resistor 25 anddiode 23. A pair of similarly poled crystal diodes 11 and 18 are connected to that same point from condensers 52 and 53, respectively. This arrangement constitutes an OR circuit which causes the regenerative amplifier to be triggered whenever an input pulse is applied to vany one of terminals A, B, or C, as shown on the bottom line of Fig. 4B. When, for example,

a positive pulse is applied to terminal A, it is passed by diode 16 without being aiected by diodes 11 and 18, which present a high impedance to it. A positive voltage is developed across resistor 25, triggering the regenerative amplifier.

The basic high-speed digital computer components shown schematically in Fig. 4A illustrate the adaptability of regenerative amplifiers embodying the present invention for such use. For aba-sic pulse repetition rate of one megacycle and :a pulse width of half a microsecond, the following list of circuit parameters may be taken as typical:

Resistor 25 Condenser 32 Condenser-s 5i, 52, 53

55,000 ohms. 0.01 microfarad. 0.01 microiarad.

Battery 51 24 volts, Resistors 58, 50, 60 10,000 ohms. Batteries 63, 6.55, 'M +24 volts. Resistors "ed, 68, 13 47,000 ohms.

The one-megacycle sine wave is applied to the clock or reset terminal oi each amplifier in order to restore the circuits to their low current states after triggering and to provide pulse standardization and control.

A block diagram of another common logic circuit to which embodiments of the present invention are readily adaptable appears in Fig. 5. A three-terminal AND circuit 8| and an amplier 4i are connected in series between the input terminals labeled A, B, and C and the output terminal. An inhibition terminal D has been added to the AND circuit. The circuit shown has an output only when all three inputs are present, and an inhibiting pulse is not.

An AND circuit with inhibition which embodies the present invention is shown in Fig. 6A. The regenerative amplifier is similar to those which have already been described, and three input terminals, labeled A, B, and C, are provided. Coupling condensers 35, 66, and 81 are connected to terminals A, B, and C, respectively, and crystal diodes 88, 89, and 90, respectively, are connected between them and the emitter of transistor Il. Each diode is poled oppositely to the direction of positive emitter current dow, forming an AND circuit. The junction between condenser 85 and diode 88 is returned to a negative potential, conventionally represented by a battery 9i, through a resistor 92. Similarly, the junction between condenser 86 and diode 39 is returned to a negative potential, represented by a battery 9 3, through a resistor 945, and the junction between condenser 31 and diode 90 is returned to a negative potential, represented by battery 95, through a resistor 96. The inhibition terminal is labeled D, and a coupling condenser 01 is connected to it, while a crystal diode SS-is connected between condenser 91 and the base of transistor il. Diode 96 is poled for easy current iiow from the inhibition terminal D toward the base, and the junction between condenser 91 and diode 98 is returned to a negative potential, represented by a battery 99, through a resistor 00. A crystal diode E0 i, poled for easy current iiow from ground toward diode S8, is connected in parallel with the series combination of resistor 00 and battery 69.

The operation of the circuit shown in Fig. 6A is iliustrated by the various wave forms shown in Fig. 6B. The three upper pulse trains represent the input signals applied to terminals A, B, and C, the fourth line illustrates the pulsesapplied to inhibition terminal D, the fifth line represent-s the output pulses generated by the transistor ampliiier, and the bottom line illustrates the wave forms appearing at the base electrode of transistor il. As has beenindicated, diodes ,88, 83, and. Si! form an AND -circuit which passes apropos ill ,ta pulse only'fwhen:onensiappliedzxto all threeiinputs. When a pulse is applied to only oneioratwo inputsthe other diodes are not cut..oi, and no pulse r,Lllpcarsat the emitter o'transistor i i. 'fis has been stated previouslyjthe Apresence of the clock pulses at the'base of transistor H not 'only serves toreset the circuitto'its low Acurrent'state after' it has beentriggeredbut also serves' to prevent the generation of pulses during intervals in which lthepositivebase pulse is present. Thus, .the regular clock pulses Vappliedtc the baseY serve '.bothtoconvert the flip-flop ,circuitY into an amplilfier and jto standardizethe generated pulses. In the circuitshown'in"Fig."6A, the property of inhibition is 'further taken advantage -oi bythe use of the inhibition terminal'D ,and Ithe associated network. As shown onthebottom line of Fig. :.SB, the ,presence of pulses at inhibition .terminal fl) serves-in effect to iillin the blanksbetween `the @regular clock or resetpulses. Inhibitioncan thus `be controlledbyanfexternal signal aswell as by the regular clock built into the system.

.,F'cr ,the same .basic `.pulse repetition rate and .pulse widthsasrused ,in thefcircuits rof Fig. 4A, :1. e,.,; afpulse repetitiontataof one -megacycleand a ulsewidth of-,half of -amicrosecond `theioliow- .ing listaof circuit parameters may .betakenfas .typicalfforthecircuitfofFig. 6A:

.Asfinithe:otheriexamplesfa.sine .wave o-.a mega- :cycle ifrequency isappliedito theclock terminal.

in. connection 'Withthe examples .of :basic 'com- 45 fputer .components .c embodying lthe present inven- A.tion :which have :been described, it 'should be rememberedzthattthe specific numbers of input terminals Vused .in the speciiic combinations o'f OR, zor inhibition :circuits shown are only 50 `represen'tative -0'f :a much larger lrange lofcombinations. -'I'hezpresent invention-maybe employed to radvantage fin .a 'large .number of high-speed .switching and computer systems as Well asin :many other Vunnamed applications.

is tobe understood uthatthe above-described Aar rangements are fillustrativeof the application of the Iprinciples c'f `the invention. "Numerous other arrangements may bedevised by those skilled in -:the iart vwithout .departing from the yspirit and =scopefoi the invention.

What is claimed'is:

\1. .A regenerative-pulse :ampliiier which comprises, 1in combination, a flip-'nop `circuit com- :prising a transistorihaving emitter, collector, and 265 ibase electrodes, a base lresistance common Vto the emitterA-base and Ithevcollec'tor-'base paths -of said transistor, -and'a resistance fand an asymmetri- -cally conducting device poled in -the direction 4of'positive emitter'currentfow connected in the 70 emitter-base .path 'to provide .an emitter `loadline for .said transistor, fcircuit means 'to supply rsignal rpulses to said emitter electrode to vtrigger fsaid fflip-iiop .circuit to fits 'high current state,

Further, it "55 SI2 :ofzpulses tofz-saiditbase electrodeto reset'saidiipfiiop circuit sito its low .currentistatefandftoegulate the output pulses producedthereby.

.2. A lregenerative pulse amplifier .Which :comprises, zin combination, a fflipfop circuit comnprising. a.'trarisistor:havingV emitter, collector,` and -base electrodes, -a'base 'resistance commonitothe emitter-basezandi the collector-basepathsj ofsai'd '.'transistor, and-a resistance Aand a lrstisonrcer1' direct VVvoltage connected iin1series between said emitter :electrode :and `said base Aresistance and -an asymmetricallyconducting Idevice -andalsecond source of direct'voltaga connected yin Cseries between said Lemitterfelectrode andlsaidibase resistance Lto :provide `ari'ernitter Yload-ElineV 2`for-said atransistor, said asymmetrically A'conducting `deyvice Abeing poled in the `directionfoipositiveeenfiittercurrent flow, vcircuit means to Supplys'ignal Kpulses to said vemitter electrode Yto Atrigger 'said iiip-'lop circuit to 'its high fcurrent -'state, -an'd Lcircuit means to `supply -a regular succession fof pulses `vto said '-base -electrode to rrreset Asaid iiip- 'flop circuit to its 'low currentstate 1 and to Vregullate the output pulses produced thereby.

3. A regenerative pulse Iamplifier which Acorinprises, in combination, a -iiip-'op Ycircuit v`comprising atransistorihaving emitter, collecton'arr'd -baseelectrodea a Lbase vresistance common '-'tosthe emitter-base and the collector-base paths o'f'sa'ii transistor, a. resistance rand fa lsource fo'f "direct voltage connected in vseries betwe'en "said em'itter aelectrode and said Abase .resistance, land t'an .-asymmetrically .conducting adevice and '.andther source 'of :direct 'voltage .also rconnected inl -series #between-said emitterrelectroile tand said base-:revesistance,` the1qu'iescent directivoltage levelf'ofisaid base electrode :being between the :respective jiliarect voltages supplied :by said :sources 4and :said :asymmetrically conductingvdevice 'beingrpole'd 1in the .direction :of positive (emitter current flow, circuitmeanstosupplysignalpulses-.to'saidemit- ,terfelectrode vto triggerv said fiiip-giiop :circuit bonits high-current1state,.and circuit means toesupply 'a-.regular succession =offpulses to said basexelec- Jtrede tosreset said.=ip-,op-circuit.to its .low current lstate .and to regulate ythe Aoutput .pulses produced thereby.

.4. .A `regenerative,pulse .amplifier .which .comprises, incombination, Y.a flip-flop -circuit 4.comprising `a transistorhaving emitter, collectoniand base electrodes, .a 4base .resistance common to .the `emitter-'base and .the collector-.base paths Lof saidtransistor, .aresistanceand-,a .rst source. of. direct voltage poled Lto bias .said emitter ielectrodejin .the iorwardvdirection connected in series between 4said emitter .electrode V.and said base resistance, and an Yasymmetrically conducting device ,pol'ed in .the direction -of positive emitter current 'fiow .and `a second source ofdirect voltagerpoled Oppo- .sitely from said first source of direct voltage connected in series between said emitter electrode and said 'base resistance, circuit'means'to supply signal pulses lto said Yemitter Aelectrode totrigger said -f1ipfl0p circuit to `its high 4current state, and circuit'means `to "supply a 'regular succession of pulses to said base Ielectrodeto reset said'ipflop circuit to its lowcurrent state Aand to regu- "late the output pulses Yproduced thereby.

y'5. A-regenerative pulse 'amplifier which -comprises, in combination, a single-transistor p- *flop circuit, circuit means to supply signal pulses 'to 'the `emitter electrode of the transistor'to trigger said flip-:flop circuit toits high current state, -and circuit means Vto Tsupply a regular succession to reset said flip-op circuit to its low current state and to regulate the pulses produced thereby.

6. A regenerative pulse amplier which comprises, in combination, a lip-op circuit comprising a transistor having emitter, collector, and base electrodes, a base resistance common to the emitter-base and collector-base paths of said transistor, a resistance and a rst source of direct voltage poled to bias said emitter electrode in the forward direction connected in series between said emitter electrode and said base resistance, and a first asymmetrically conducting device poled in the direction of positive emitter current flow and a second source of direct voltage poled oppositely from said rst source of direct voltage connected in series between said emitter electrode and said base resistance, circuit means including a second asymmetrically conducting devicepoled in the direction opposite to that of positive emitter current flow to supply signal pulses to said emitter electrode to trigger said ip-iiop circuit to its high current state, and circuit means to supply a regular succession of 14 pulses to said base electrode to reset said flipflop circuit to its low current state and to regulate the output pulses produced thereby.

7. In combination, a regenerative pulse amplier comprising a single-transistor flip-flop circuit, circuit means to supply signal pulses to the emitter electrode of the transistor to trigger said flip-flop circuit to its high current state, and circuit means to supply a regular succession of pulses to the base electrode of the transistor to reset said ip-flop circuit to its low current state and to regulate the pulses produced thereby, and circuit means to supply pulses to the base electrode of the transistor in the intervals between regular base pulses to prevent the generation of pulses by said amplier.

JEAN I-I. FELKER.

Name Date Moore Nov. 21, 1950 Number 

